Movable bushing for pressure loaded gear pumps



June 23, 1959 J. F. MURRAY 'ETAL 2,891,433

MOVABLE BUSHING FOR PRESSURE LOADED GEAR PUMPS Filed April 13, 1956 M -2Sheets-Sheet 1 EYE 27227775 7 John F Murray 5% 44W, aw 22 253;

1959 J. F. MURRAY ETAL 2,891,483

MOVABLE BUSHING FOR PRESSURE LOADED GEAR PUMPS Filed April 13, 1956 2Sheets-Sheet 2 Ezra firm 15E c/ofuz F Murray nited States 2,91,483Patented June 23, 1959 This invention relates generally to gear pumpsand more particularly relates toimproved means for hydrostatically andhydro'dynamically lubricating and balancing a bearing bushing means in apump.

Although the principles ofthe-p'resent invention are of generalutility;particularlymseful' application is made in connection withaircraft fuel-pumps; Oneof the major problems in" the manufacture andconstruction of aircraft fuel'pumps handling-gasoline and other fuelcompounds has been in the satisfactory hydrostatic and hydrodynamiclubrication andbalancing of-thebearing end platemeansused in journallingand sealing the rotatable fluid displacement means of the fuel pumps. Inthis connection, the problem becomes particularly acute because the fuelcompounds forming thepumpingmedium have viscosities which are farlessthan the "viscosities offluids normally handled 'by hydraulic .pumps :ofconventional design. Accordingly, the present invention contemplates theprovision of a lubricatingrand balancing arrangement which will functionefficiently: even though'the pump, speeds and pressures increaseandthetemperature of the working fluid'iises.

It is an object of the present invention to'provide'improved meansfor-hydrostatically andhydr'odynamically lubricating and balancing.bearing end plate-'means in a pump.

Yet another object 'ofthezpresentinvention is -to-provide improved imeans for obtaining: satisfactory "lubrication and heat dissipation -atbearing and journalling surfaces ina pump handling low viscositywork-ingfiuids. I

Yet another object ofthe presentinventio'n is toprovide afuelpump:-ofincreased capacity.

- Many other features;advant agesand additional objects ofthenpresent-invention-will become manifest to those versed in the artupon -makingi reference to the detailed description which followsand--the -aecompanying;she'ets of drawings' in-whicha preferredstructural embodiment of=a-3pump.-incorporating thQ PIlnCiPICS Of thepresent inventiorris--shW11 by-Way0f illustrative example.

Onthe drawings: 7 p

Figure 1 -is a cross-sectional -viewof aepressure-loaded gean-purnpembodying the principles of' the present invention; V

Figure-2 is 'a fragmentary cross-sectional view reduced in size' andtaken substantially on line lI=---II of Figure 1;

Figure 3 is- 'aside elevational view of the bearing end plate -rneans=provided in accordance with the principles -Ofithe present invention; 7I

Figure-4 is an end-elevational iew of the'bearing: end plate means of-Figure-B; I

Figures 5,"6, 7 and-8 are perspective views "of bearing end plate-meanssimilar to the bearing-endplatemeans of -Figures 3 "and 4 -butillustrating different forms of the present invention.

As sh'ow n on the-drawingsz- V For-clarity and understanding, theprinciples 'of the present invention are illustrated in connection witha pressure-loaded gear pump indicated generally at 10.

The pump 10 includes a-casingi'll having formed therein an inlet '12andan: outlet 13 communicating" with apumping chamber 14" in which-isrotated arotary fluiddisplacement means taking the form ofa drivergear*16 and a driven gear'17.

Each of the gears 1 6and -17 have gear shaft extensions indicated at 18and 19, respectively, :by means of which the gears may befiournalled forrotation'in the casing 11. On the-driver gear 16,-.the gear shaftextension includes a coupling portion 19 splined" to a 1 driver member20 which is adapted tobe connected to'asuitable source of driving power.A suitable--bearingi and sealing means indicated generally 'at 21 isretained inthe casing'll by.

a cover member "22. It will be understood-thatsuitable recesses andO-ring sealing :members' maybe providedthroughout thepumptoestablishthe-necessary seals-between'adjoining surfaces 'ofthepump -components.

A -portio'n of the "casing -11 has bearing surfaces formed therein for--corresp'onding -.-gear shaft --extens'i'ons 18"and-19 on the driveranddrivemgears 16and--17-and such bearing surfaces are indicated =-by-thereference numeral 24 and-26, respectively; The casing'i-further providesa stationary sealing surface-27 for Y sealing and engaging against-anadjoining' side face of a corresponding -gear'16'or 17.

Ontheopposite side of -the gears 16 and-'17, there "is provided amovablepressure-loaded bushing indicated generally -at-' 28, one bushing-:28being provided for each corresponding-gear- 16 and-17. Each ofthebushings 28 has corresponding structural features and, accordingly; onlya-single'set of referencenumerals will beempl'oyed in-referring to theseparate bushings.

The bushings 28*constitute =bearing-end-plate means and each bushing28-c onsists of "a generally tubular article including a cylindricalbody portion -29*having a bore extending therethrough :and forming acylindrical bearing surface 30 for rotatably journallingagear-shaftextension-18 or 19 of the driver gear -1'6-*and--1'7, respectively. H

At one end of-each bushing: 28, there is :provided a radially outwardlyextendingfiange 31. The front-face of the flange 31 is in'dicated-at 32;and constitutesasealing surface for engaging an"adjoining side-face ofone of thegears lfi and 17. The rear face of the-flange is indicatedat33 and is aXially'spaced-from the -'front face 32. The -pressure forcesacting on: the-front face or sealing surface 32-of--the bushing-28-varybetween a minimum at the inlet side of the pump to,- a 7 maximum at theoutlet side of-the.-pump. Accordingly, the'back surface 'or motivesurface *33 -on thebushing-128 is arranged to increase proportionatelyin area frorn'the pump inlet to the-pump outlet-for balancing:theunequalpressure forces inthe pumping chamber. In this connection, the tubularor cylindrical extension 29 of the bushing-28 is generally concentricwith respect to the flange-31, however, theperipheral surface of thebody portion -29 is interrupted by a shoulder 34 which is eccentrically'offset towards "the inlet side of thepump, therebyproviding a motivesurface 33 with a generally circular outer speriphery 36 and agenerallyfcircular-inner.:periphery 37, the "inner periphery beingeccentrically disposed with respect to the axis of thebushingZS'tO-thereby provide a major area on the discharge side ofthepump'anda minor area on the inletside of the-pump. In other words-,theshoulder 34 has the effect-of decreasing the extent of exposedsurface'areaon the motive surface-33 in the region of thepump-inlet.Means are-provided to communicate .pressuregenerated by the pumpbehindthe motive surface 33' and in this connection it maybe noted that suchmeans are provided it in the present illustrative exampleby formingwanopening--38 "extending .axially through the flange 31 at the dischargeside of the pump,

It may be noted that the motive surface 33 is spaced from an adjoiningend wall 39 provided by the casing 11 and, accordingly, the back face ofthe flange 31 together with means including the wall 39 of the casing 11forms a pressure control chamber 40 to receive the pressure generated bythe pump communicated therethrough by the opening 38.

In assembly, the casing 11 has a bore 41 receiving the body portion 29of the bushing 28 and a counterbore 42 receiving the shoulder 34. Alarge counterbore 43 receives the flange 31. A recess 44 seats an O-ringsealing member 46, thereby isolating the pressure control chamber 40 byestablishing a seal between the peripheral surface of the shoulder 34and the casing 11. Those versed in the art will recognize that the bore41 and the counterbore 43 are in concentric relation with respect to oneanother so that all critical dimensions can be maintained with greatconvenience. The counterbore 42 which must be eccentrically oflset neednot be located with extremely great accuracy because manufacturingtolerances are readily compensated for by virtue of the flexibilityafforded through the utilization of the -O-ring sealing member 46between the casing 11 and the annular eccentrically offset shoulder 34.

It will be noted that the gears 16 and 17 have bores extendingtherethrough as indicated at 47 and 48. Moreover, the casing 11 isrecessed as at 49 and 50, all of these hollow spaces being communicatedwith the pump inlet, thereby to maintain low pressure throughout thepump to facilitate the use of low pressure seals.

Spring means are provided to initially load the movable bearing endplate means into sealing engagement with the gears 16 and 17. In theform of the invention herein illustrated, the motive surface 33 ischaracterized by the formation therein of a plurality of recesses 51bottoming coil springs 52 and engaging the wall 39 to establish acontinuous biasing force urging the bushings 28 in the direction of thegears 16 and 17.

Referring now more particularly to Figures through 7, the improved meansfor hydrostatically and hydrodynamically lubricating and balancing thebushings 28 will be described in detail.

In Figure 5, the sealing surface 32 has a relief recess 53 formedtherein on the inlet side of the bushing 28, thereby to facilitate andassist in filling the spaces between the gear teeth with fluid.

On the outlet side of the bushing 28, the sealing surface 32 isparticularly characterized by a chamfered recess 54 which extendstangentially and improves the discharge characteristics of the pump. Thesurface 32 is further characterized by a trapping relief recessindicated at 56 and located on the discharge side. The trapping relief56 affords relief against fluid being trapped by the intenneshing of thegear teeth on the driver and driven gears 16 and 17 in the vicinity ofthe pump discharge or outlet 13.

It has been determined that operation of the rotary fluid displacementmeans or the gears 16 and 17 results in a shifting of the point of loadconcentration towards the inlet side of the bearing surface 30. In otherwords, during operation of the pump, there is a critical bearing area ofcontact which is subjected to a concentrated load during operation ofthe pump. This critical area appears to be shifted towards the inletside of the pump. Using the orientation of Figure 5 and considering theannular bearing surface 30 as being disposed with reference to a systemof rectangular coordinates with the associated gears rotating inclockwise direction, the critical area of load concentration is locatedin the lower left quadrant. It is contemplated, according to the presentinvention, there fore, to establish a system of recesses or a groovepattern formed to provide a fluid reservoir at the critical area of loadconcentration. In the embodiment of Figure 5, the groove patterncomprises a single, longitudinally extending groove 57 which terminatesat 58 and at 59 short of the opposite ends of the bearing surface 30. Agroove or passageway 60 communicates pressure generated by the pump tothe reservoir formed by the groove 57, thereby to assist in thedissipation of heat from the critical area of load concentration as wellas to lubricate the bearing surface 30 at this critical area. Thepassageway 60 is provided with a metering orifice 61, thereby topreclude excessive flow at high discharge pressure and it will beunderstood that the bearing areas 62 and 63 at the bearing surface 30adjoining the ends 58 and 59 of the groove 57, respectively, will havethe effect of limiting the outward flow of fluid from the reservoir,thereby permitting fluid to be bled out of opposite ends of thereservoir or groove 57 to flow circumferentially around the journallingand bearing surface 30.

In the form of the invention illustrated in Figure 5, the passageway 60extends axially and communicates with a groove 69a formed in the sealingsurface 32 and intersecting the chamfered discharge recess 54, therebycommunicating full discharge pressure into the reservoir 57.-

There is also provided, in accordance with the principles of the presentinvention, a circumferentially dis continuous counterbore 64circumjacent the bearing surface 30 and formed in the sealing surface32. The counterbore recess 64 has its opposite ends indicated at 66 and67, respectively, spaced apart from one another by portions of thesealing surface 32 indicated by a separate reference numeral 68. Thesealing portions 68 are located axially opposite the critical area ofload concentration. Thus, the counterbored recess 64 extends around thebearing surface 30 at the portions under lesser load concentration. Fulldischarge pressure generated by the pump is communicated into the recesscounterbore 64- by a metering passageway 69 extending between the recess64 and the trapping relief 56.

The sealing surface 32 of the bushing 28 illustrated in Figure 5 isfurther characterized by the provision of a segmental arcuate groove 70.The groove 70 is located concentrically outwardly of the counterborerecess 64 and preferably outside of the root diameter of the gear teethon the gears 16 and 17. v The groove 70 extends from the chamferedrecess 54 and thereby communicates pressure generated by the pump fromthe outlet side of the bushing 28 towards the inlet side. The groove 70therefore has the effect of communicating fluid at increased pressure tothe spaces between the gear teeth towards the inlet side of the pump andthereby distributes the forces acting on the sealing surface 32.

In Figure 6, the bushing is indicated at 28a and parts which are similarin function to corresponding parts of the bushing 28 of Figure 5 areindicated by similar reference numerals bearing the sufl'ix A. In thisform of the invention, the reservoir or groove is indicated at 57a andfluid at discharge pressure is communicated thereto by means of ametering orifice 61a communicat ing to a pressure control chamber 40 ata point adjacent the motive surface 33, for example, as is more clearlyindicated in Figure 4. In the form of the invention indicated in Figure6, the counterbored recess 64a is circumferentially continuous and fluidat discharge pressure is communicated thereto by means of the passage69a communicating with the trapping relief 56a.

In the embodiment of Figure 7, the bushing is indicated at 2811. Thereservoir or groove 57b corresponds to the groove 57a of the embodimentof Figure 6 and a metering opening 61b communicates fluid at dischargepressure thereto. A circumferentially continuous counterbored recess 64bis formed in the sealing surface 32b circumjacent the bearing surface30b. concentrically outwardly of the counterbored recess 64b is providedan annular row of separated pockets each indicated at 71. Eachrespective pocket 71 communicates with pressure generated by the pump bymeans of a passageway 72 extending between a corresponding pocket 71 andthe counterbored. recess 64b. Aspassage 69b communicatespressure-generated bythe pump" from the trapping relief 56b to thecounterbored recess 64b. --By communicating workingrfiuidat dischargepressure individuallyto the separatedpockets-through a plurality ofmetering-orifices, a more uniform and positive lubrication film isspread over the-entiresealing surface- 32b. It -will be -understood thatthe working fluidwillpass through the leakage; paths over the'entireface provided by the sealing surface 32b.

Inithe'em'bodiment of Figure 8, the' bushing isindicated bythe reference*numeral 280; In this form: of the invention, thergroovepattern-includes 'a-longitudinally extendinggroove '7c andalsoaiplurality of circumferentially extending lateral grooves 73 whichare-formed in the bearing surface 300 and which intersect thelongitudinal groove"57'c,"thereby to 'providea'plurality of pocketswhich will have theeifect of more rapidly distributing working fluid inthe critical area of bearing-icontact. Working fluid at pressuregenerated by the pump is communicated to the pattern of-grooves by ametering opening 610 communicating with the pressurecontrol chamber 40,-The sealing face 32c also has a circumferentially continuous recess 64ccommunicating with full discharge pressure through thefpassageway 690.It should-be understood that the shape and the position of the groovepattern may be otherwise varied and modified. according to thevarying'lubrication andcooling demands which are placed upon the pump bythe operating requirements thereof.

In each-of the arrangements described, it will be 'appreciate'd thatthere is provided a lubrication system wherein" the working fluid iscommunicated to the critical "area of load concentration at a flow ratewhich is proportioned to the pump discharge: pressure and in" suchaFmanneras tovprevent excessive flow-at highdischarge pressures.'Moreovenby virtue of the provision thus made, vlower bearing clearancesmay be provided since heat dissipation is improved andthe'location ofpockets of 'flui'dfat-high.pressure at localized-areas on differentportions of the bushing hasthe effect of hydro'statically and.hydrodynamically lubricating and balancing the bushing.

Althoughivarious. minor modifications might be' suggested by II thoseversed .in..the art, it should be understood that we Wish to embodywithin the scope of the patent warranted hereon all such modificationsas reasonably and properly come within the scope of our contribution tothe art.

We claim as our invention:

1. A fluid pump of the type including a housing having an inlet and anoutlet, a rotatable pumping member journalled in said housing fortransferring fluid from said inlet to said outlet, axially movable endplate means adapted to engage said pumping member in sealing relationand movable independently of said rotatable pumping member, a continuousgenerally annular motive surface on said end plate means adapted inresponse to application of pressure thereto to urge said end plate meanstowards said rotatable member to establish said sealing relation,conduit-defining means for continuously communicating pressure generatedby said pump to said motive surface, said motive surface having agenerally circular outer periphery concentrically disposed with respectto the axis of rotation of the pumping member and a generally circularinner periphery eccentrically disposed with respect to the axis of saidpumping member, said inner periphery having its center offset towardssaid inlet port, a general ly annular sealing surface on said end platemeans to engage an adjoining side face of said rotatable member, a boreformed in said end plate means and extending therethrough concentricallyof said sealing surface and providing a bearing surface for journallingsaid rotatable member, a counterbore formed in said sealing surface,means communicating pressure generated by said pump to said counterbore,a plurality ofpockets formed in said sealing-surface in anannular rowconcentrically outwardly, ofsaid -counterbore, eachpocket havingmeanscommunicatingpressuregenerated by said pump; to a corre sponding pocket,thereby to establish a uniform distribution of lubricant filmover theentire sealing surface.

2. fliiidpunip of. the type including a housing having aninlet a'nd:anbutlet, arotatable pumping member journaled inrsaid housing fortr-ansferringfiuid from the inlet to the outlet, axiallymovable endplate means adapted to engage said'pumpingv member in sealing relationand movable independently of said rotatable pumping member, a continuousgenerally annular moti've surface on said endplate means adapted. inresponse to application of pressure theretoto urge said end plate meanstowards said rotatablewmember to establish said sealing relation,conduit-definingmeans for continuously communicating pressure generatedby said .pump to said motive surface, a generallyar'mular; sealing.surface on said end plate means to engage an adjoining. side-face ofsaid rotatable memberto establish saidseal relation, a bore formedinsaid end-plate means'and extending. therethrough concentrically'of-saidsealing surface andproviding a bearing surface for. journalingsaid rotatable member, said bearing surface havingv localized recessmeans formed therein offset towards the inlet side of the pump andproviding a reservoir at the center of load concentrationproduced bypump generated pressures acting on the rotatable pumping membergsaidrecess means consisting of a groove pattern loeatedin acriticalareaof load contact axially opposite the center of load concentrationproduced by the pump generated pressures acting on the rotatable pumpingmemberwhensaid-rotatable member-is rotated at operating speed-and nieanscommunicating pressure generated by the pumpinto said reservoir tohydrostaticall-y and hydrodynamically lubricate said bearing surface.

3. A fluid-pump as defined in claim 2,said sealing surfacehaving atrappingrelief formed therein at the discharge sidethereof; and agroove'formed in said end' plate meansextending-between said recessmeans andsaid trapping relief to provide said means for communicatingpressure generated by thepump into said reservoir.

4.-A fluid pump as defined in claim 2, said end plate meanshavingagroove formed therein extending between said recess means to a. pointadjacent saidmotive surface, thereby to provide said means forcommunicating pressure generated by said pump to said reservoir.

5. A fluid pump as defined in claim 2, said groove pattern consisting ofa single longitudinally extending groove terminating short of oppositeends of said bearing surface.

6. A fluid pump as defined in claim 2, said groove pattern consisting ofat least one longitudinally extending groove terminating short of theopposite ends of said bearing surface and at least one laterallyextending circumferentially discontinuous groove intersecting saidlongitudinal groove, thereby to form a plurality of pockets at thecritical area of load contact.

7. In a high pressure pump, a housing having an inlet and an outlet andproviding a pumping cavity, rotary fluid-displacement means in saidpumping cavity for moving fluid from said inlet to said outlet, andbearing end plate means for said cavity in said housing, said bearingend plate means having a bearing surface for journalling said rotaryfluid-displacement means, a sealing surface for engaging an adjoiningside face of said rotary fluiddisplacement means, and a pressurereceiving back surface forming together with means including a portionof said housing a pressure controlchamber, said bearing surface beingsubject to load produced by pump-generated fluid pressures acting on therotary fluid displacement means and having a center of loadconcentration shifted to one side when the rotary fluid-displacementmeans is operated and having a groove pattern formed therein at saidcenter of load concentration to provide a reservoir, said sealingsurface having a plurality of pockets disposed in an annular row andmeans placing said pressure control chamber, said reservoir and all ofsaid pockets in pressure communication with said outlet, thereby tohydrostatically and hydrodynamically balance and lubricate the bearingend plate means.

8. In a high pressure pump, a housing having an inlet and an outlet andproviding a pumping cavity, rotary fluid-displacement means in saidpumping cavity for moving fluid from said inlet to said outlet, andbearing end plate means for said cavity in said housing, said bearingend plate means having a bearing surface for journalling and supportingsaid rotary fluid-displacement means, a sealing surface for engaging anadjoining side face of said rotary fluid displacement means and apressure-receiving back surface forming together with means including aportion of said housing a pressure control chamber, said bearing surfacebeing subject to load produced by pumpgenerated fluid pressures actingon the rotary fluid dis placement means and having a center of loadconcentration shifted to one side when the rotary fluid displacementmeans is operated and having a groove pattern formed therein at saidcenter of load concentration to provide a reservoir, said sealingsurface having a circumferentially discontinuous recess formed thereincircumjacent said bearing surface, said recess being discontinuous atthat portion of said sealing surface axially opposite the center of loadconcentration, and means communicating pres sure generated by said pumpinto said pressure control chamber, said reservoir, and said recess,thereby to hydrostatically and hydrodynamically balance and lubricatethe bearing end plate means.

9. In a high pressure pump, a housing having an inlet and an outlet andproviding a pumping cavity, rotary fluid displacement means in saidcavity for moving fluid from the inlet to the outlet, and bearing endplate means for said cavity in said housing, said bearing end platemeans having a bearing surface for journallin-g said rotary fluiddisplacement means, a sealing surface for engaging an adjoining sideface of said rotary fluid displacement means, said bearing surface beingsubject to load produced by pump generated fluid pressures acting on therotary fluid displacement means and having a center of loadconcentration shifted towards the inlet side of said bearing means, andrecess means in said bearing surface forming a reservoir at said centerof load concentration, and means communicating pressure generated bysaid pump into said recess means, said sealing surface having asegmental circumferential groove circumjacent said bearing surface, saidsealing surface having a sealing area formed between opposite ends ofsaid segmental groove axially opposite said center of loadconcentration, and means communicating pressure generated by said pumpinto said recess and into said segmental groove.

10. In a high pressure pump as defined in claim 9, said sealing surfacehaving a second segmental groove formed therein concentrically outwardlyof said first mentioned segmental groove and extending from thedischarge side of said bushing means towards the inlet side of the pumpto distribute the pressure forces acting on said sealing surface.

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